Integrated Electrode Design Enables Ampere-Level CO2 Electroreduction in Aqueous Electrolytes

Abstract Gas-fed CO2 reduction reaction (CO2RR) electrolyzers suffer from inherent salt precipitation and performance decay due to hindered salt removal within electrodes. Although electrolyzers that reduce CO2 carried by aqueous electrolytes (e.g., H-cells) naturally avoid salt accumulation, their low CO2 solubility and sluggish mass transport restrict current densities to typically <0.1 A cm–2. Here, resolving the electrode–transport mismatch is shown to be the key factor for enabling ampere-level electrolyte-fed CO2RR. In a pressurized zero-gap electrolyzer, where CO2 is supplied by a flowing aqueous electrolyte, the conventional layered electrode is reconstructed into a hierarchically porous integrated electrode by directly growing Ni single-atom-anchored CNT arrays on carbon fiber paper. The interconnected micrometer-scale pores facilitate the transport of CO2-saturated electrolytes throughout the electrode thickness while maintaining high intrinsic catalytic activity. Under a CO2 pressure of 0.5 MPa, a CO partial current density of 0.760 A cm–2 is achieved, representing a 3.67-fold enhancement compared with the conventional layered electrode under identical pressure. Operando impedance and voltage loss analyses reveal that the integrated structure reduces concentration polarization by 37%, confirming that improved CO2 accessibility within the electrode is decisive for high-rate operation. This work establishes a general electrode design principle for enabling ampere-level electrolyte-fed CO2RR, providing a scalable pathway toward stable CO2 electrolysis.